Brontosaurus, I remember the name change quite some time ago. Wasnt absolutely sure, but I figured it was probably the right one
Heaviest noble gas. Well Radon is the radioactive gas that comes into your house (sometimes), and radioactivity is associated with the heaviest elements.. so that should be the one...
CH4 and natural gas.. I remember all the jokes about farts, natural gas, and methane, so methane was the pick.
Eukaryote by early memory and elimination
1 newton through 1 meter. Force thru a distance is Energy, thats joule, watt is energy/time.
DNA nucleotide, I remember there was one that started with a T, thus Thiamine.
K in periodic table, I take this supplement sometimes and buy it from the drug store, often listed under K - potassium.
1 Newton on 200 gram object. F=ma, so a=F/m = 1kg-m/s^2/.2kg=5m/s^2=5 meters per second squared.
Demotion of Pluto, Ceres=asteroid and Charon=plutos moon. Between Eris and Nyx, Eris sounded familiar.
Quark, I knew came from a non scientific reference, not sure which it was, also, by elimination.
Coefficient of friction, remembered my engineering classes, also by elimination.
Mitosis vs Meiosis, I was leaning towards mitosis. Took that guess.
Lightest halogen, fluo, as in fluid (or stream, or "move freely").
Triangle, unequal lengths. By elimination.
Plank or Heisenburg? I was "uncertain" about this, until I remembered about the Plank Constant.
Nimbus. I clearly remember about cumulonimbus clouds making rain.
Moons around Saturn or Jupiter. I remember Io and its volcanoes, orbiting around Jupiter.
James Watt, BTU or HP? Took a guess, but was leaning HP anyways.
Latin for potassium bearing rocks is Kallium. Just like sodium is Natrium, so we use Na in the periodic table. Plumbum for lead, same difference.
I studied ALOT of chemistry in HS, then alot of physics and CS in college.
LOL thats why I picked methane, thought of cow farts...
BTU is a unit of heat (like the calorie and the Joule), not a unit of power (Watt or horsepower). I answered most of the questions using the same logic as you did.